Fakultet for naturvitenskap og teknologi: Recent submissions
Now showing items 2421-2440 of 5371
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Biomarker and isotopic composition of seep carbonates record environmental conditions in two Arctic methane seeps
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-12)Present-day activity of cold-seeps in the ocean is evident from direct observations of methane emanating from the seafloor, the presence of chemosynthetic organisms, or the quantification of gas concentrations in the water column and pore water solutes. Verifying past cold seep activity and biogeochemical characteristics is more challenging but may be reconstructed from proxy records of authigenic ... -
CO2 Increase Experiments Using the CESM: Relationship to Climate Sensitivity and Comparison of CESM1 to CESM2
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-14)We examine the response of the Community Earth System Model Versions 1 and 2 (CESM1 and CESM2) to abrupt quadrupling of atmospheric CO2 concentrations (4xCO2) and to 1% annually increasing CO2 concentrations (1%CO2). Different estimates of equilibrium climate sensitivity (ECS) for CESM1 and CESM2 are presented. All estimates show that the sensitivity of CESM2 has increased by 1.5 K or more over that ... -
Vibrational spectroscopy beyond the harmonic approximation with the Polarizable Embedding model
(Doctoral thesis; Doktorgradsavhandling, 2021-02-23)In order to efficiently and accurately calculate vibrational properties for solvated systems, a theoretical framework for combining response theory with the Polarizable Embedding model (PE) has been derived and implemented, and is presented in this thesis. An open-ended recursive formalism is utilized through the implementation in OpenRSP, allowing energy-derivatives to be calculated analytically ... -
Environmental variability off NE Greenland (western Fram Strait) during the past 10,600 years
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)To reconstruct the climatic and paleoceanographic variability offshore Northeast Greenland during the last ~10 ka with multidecadal resolution, sediment core PS93/025 from the outermost North-East Greenland continental shelf (80.5°N) was studied by a variety of micropaleontological, sedimentological and isotopic methods. High foraminiferal fluxes, together with high proportions of ice-rafted debris ... -
Dinocyst stratigraphy of the Valanginian to Aptian succession (the Rurikfjellet and Helvetiafjellet formations) from Spitsbergen, Norway
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-11)In order to improve the understanding of how the high northern latitudes responded to the escalating warming which led to the middle Cretaceous super greenhouse climate, more temperature proxy records from the High Arctic are needed. One of the current obstacles in obtaining such records is poor age control on the Lower Cretaceous strata in the Boreal region. Here, we provide a biostratigraphic ... -
Passive seismic recording of cryoseisms in Adventdalen, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-20)A series of transient seismic events were discovered in passive seismic recordings from 2-D geophone arrays deployed at a frost polygon site in Adventdalen, Svalbard. These events contain a high proportion of surface wave energy and produce high-quality dispersion images using an apparent offset re-sorting and inter-trace delay minimisation technique to locate the seismic source, followed by ... -
Thermal Characterization of Pockmarks Across Vestnesa and Svyatogor Ridges, Offshore Svalbard
(Journal article; Tidsskriftartikkel, 2020-11-10)The Svalbard margin represents one of the northernmost gas hydrate provinces worldwide. Vestnesa Ridge (VR) and Svyatogor Ridge (SR) west of Svalbard are two prominent sediment drifts showing abundant pockmarks and sites of seismic chimney structures. Some of these sites at VR are associated with active gas venting and were the focus of drilling and coring with the seafloor‐deployed MARUM‐MeBo70 ... -
Evolution of a shear zone before, during and after melting
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-03)Partial melt in the deforming mid- or lower continental crust causes a strength decrease and drives formation of lithological heterogeneities. However, mechanisms of formation of syn-melt deformation zones and strain partitioning in partially molten rock remain poorly understood. We use field and microstructural observations to unravel the evolution of a partial melt shear zone, Seiland Igneous ... -
Klimanøytral miljøpark – en vurdering av kostnader og nytteverdi for klimagassreduserende tiltak
(Master thesis; Mastergradsoppgave, 2020-12-14)Remiks AS har gjennom flere år gjort en kartlegging av klimagassutslipp knyttet til egen virksomhet. På bakgrunn av dette er det iverksatt flere tiltak på aktuelle områder som har blitt identifisert. Det er i midlertidig ikke sikkert at investeringene som er gjort er de mest effektive tiltakene om man vurderer kostnadene mot klimanytten. Denne studien vil vurdere tiltakene solenergi, biodrivstoff, ... -
Wideband Self-Interference Cancellation Using Multi-Tap Filter in Radar Front End
(Mastergradsoppgave; Master thesis, 2020-12-14)The largest hurdle in full duplex wireless systems is the self-interference introduced by the transmitted signal into the received signal. In multi antenna systems this interference is caused by the direct coupling between the transmitting and receiving antennas. In systems where the transmitter and receiver uses the same antenna the interference is caused by inadequate isolation between the ... -
Performance and Future Potential of Solar Photovoltaics in Arctic Settlements
(Master thesis; Mastergradsoppgave, 2020-12-15)Data from a solar photovoltaic (PV) installation on Svalbard Airport Longyear has been analyzed to investigate performance of solar photovoltaics in the Arctic. Results show that the average capacity factor at the facility is 5.6 % after its first two full years of production. While the production in the winter is zero, monthly capacity factors are observed to be as high as 16 % in the summer. On ... -
Towards detection and classification of microscopic foraminifera using transfer learning
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-06)<p>Foraminifera are single-celled marine organisms, which may have a planktic or benthic lifestyle. During their life cycle they construct shells consisting of one or more chambers, and these shells remain as fossils in marine sediments. Classifying and counting these fossils have become an important tool in e.g. oceanography and climatology. <p>Currently the process of identifying and counting ... -
The Raunis section, central Latvia, revisited: first luminescence results and re-evaluation of a key Baltic States stratigraphic site
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-08)In interstadial deposits, sand interbeds gain limited consideration in comparison with organic sediments, and therefore tend to be underrepresented in paleoenvironmental reconstructions. The Raunis site, central-eastern Latvia, is an example where organic beds have already gained some attention and been used to understand the complex interactions between advance and retreat of the Scandinavian Ice ... -
Neodymium isotope constraints on chemical weathering and past glacial activity in Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-15)<p>Neodymium (Nd) isotopes in leached authigenic components of marine sediments have been increasingly used as a tracer of past ocean-water masses. Despite the general assumption that the Nd isotopic composition of solutes released during chemical weathering fingerprints the source rocks on continents, preferential dissolution of easily dissolvable phases may result in significant deviations in Nd ... -
The role of shelf morphology on storm-bed variability and stratigraphic architecture, Lower Cretaceous, Svalbard
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)The dominance of isotropic hummocky cross‐stratification, recording deposition solely by oscillatory flows, in many ancient storm‐dominated shoreface–shelf successions is enigmatic. Based on conventional sedimentological investigations, this study shows that storm deposits in three different and stratigraphically separated siliciclastic sediment wedges within the Lower Cretaceous succession in ... -
Miocene Seep-Carbonates of the Northern Apennines (Emilia to Umbria, Italy): An Overview
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-28)The natural emission of methane-rich fluids from the seafloor, known as cold seepage, is a widespread process at modern continental margins. The studies on present-day cold seepages provide high-resolution datasets regarding the fluid plumbing system, biogeochemical processes in the sediment, seafloor seepage distribution and ecosystems. However, the long-term (hundreds of thousands to millions of ... -
Exhumation of the High‐Pressure Tsäkkok Lens, Swedish Caledonides: Insights From the Structural and White Mica 40Ar/39Ar Geochronological Record
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)Integrated structural, geochemical, and geochronological investigations were conducted on metasedimentary rocks in the eclogite-bearing Tsäkkok Lens of the Seve Nappe Complex (Scandinavian Caledonides) to resolve its exhumation history. Three deformation events are defined. D1 is likely related to the prograde to peak-metamorphic stages, represented by a locally preserved S1. D2 resulted in vertical ... -
Feasibility of using the P-Cable high-resolution 3D seismic system in detecting and monitoring CO2 leakage
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-01-23)The P-Cable technology is an acquisition principle for high-resolution and ultra-high-resolution 3D seismic data. Many 3D seismic datasets have been acquired over the last decade, but the application in time-lapse studies for monitoring of CO2 storage is a new and intriguing topic. High-resolution 3D (HR3D) seismic has the potential to detect and monitor CO2 leakage at carbon capture and storage ... -
Silicon substrate significantly alters dipole-dipole resolution in coherent microscope
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-16)Considering a coherent microscopy setup, influences of the substrate below the sample in the imaging performances are studied, with a focus on high refractive index substrate such as silicon. Analytical expression of 3D full-wave vectorial point spread function, i.e. the dyadic Green's function is derived for the optical setup together with the substrate. Numerical analysis are performed in order ... -
Deep learning architecture “LightOCT” for diagnostic decision support using optical coherence tomography images of biological samples
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-13)Optical coherence tomography (OCT) is being increasingly adopted as a label-free and non-invasive technique for biomedical applications such as cancer and ocular disease diagnosis. Diagnostic information for these tissues is manifest in textural and geometric features of the OCT images, which are used by human expertise to interpret and triage. However, it suffers delays due to the long process of ...